What Is a Hex Cap Screw?

A hex cap screw is a threaded fastener with a hexagonal-shaped head. While the term hex head screw is generally used interchangeably with hex bolt, these two fasteners are actually very different. Hex screws are typically smaller than hex bolts, but this is not always the case. A hex cap screw can be significantly larger than a hex bolt depending on the applications, so it's important for users to learn the identifying features of each in order to choose the correct fastener for each job.

The hex cap screw features a six-sided head, which is designed to be tightened using a wrench or drill. When used with a nut, these screws can also be tightened by hand as the nut is turned. Unlike a hex bolt, a hex cap screw does not always require a nut. A hex bolt always requires a nut, and thus must be installed by tightening the nut.

These screws can be used in a variety of manufacturing and industrial applications. They are used to join wood, metal, and composite materials. Typically, hex screws are used in projects where precision is valued above strength and mechanical performance. With no nut required, they can be used in smaller areas where a hex bolt would not fit easily. Hex bolts are generally reserved for construction purposes, such as joining wood or metal beams.

A hex cap screw is threaded all the way up the shank, and has a round washer built in just under the head. Hex bolts are only threaded along part of the shank, and do not have a washer at the base of the head. The tip of the hex head screw may be flat, pointed or chamfered, while hex bolts only feature flat heads.

These fasteners can also be identified by differences in their construction. While a hex head screw is produced through a hot forging process, bolts are generally cold rolled. This may lead to seams along the head of the bolt, while screws will never have a seam.

Users should compare different hex cap screw materials to find the best for each application. Steel is the most common material for general-purpose use, while stainless or galvanized steel holds up better in outdoor or marine applications. Brass screws may be chosen for their appearance, particularly in homes or buildings with existing brass hardware. It's also important to choose screws of the right length and diameter to safely join materials to meet the demands of the project.